Rosette Nebula
(NGC 2237, 2238, 2239 and 2246)

An emission nebula in the constellation
Monoceros, surrounding a young open cluster of stars (NGC 2244).
It is roughly circular in shape, with a central hole cleared of
dust and gas by the pressure of radiation from the stars in the
cluster. The nebula's distance is estimated to be 4,500 light
years.